Let me take two other examples, for my own convenience:
I had him doing sit-ups.
I had him do that for my entertainment.
It's idiomatic. The word 'had' doesn't have its normal meaning in the sentence. Its meaning becomes something like "I requested that he do that". To me, the 1st sentence does not imply a command, rather a neutral statement or a request. (I had him helping me / doing sit-ups).
"I had him help me / I asked him to help me." implies a command: "I ordered him to help me."